D. Graham Burnett at Cabinet:
Throwing confetti is not an exact science, and neither is philology. But the latter comes closer. Confetti hails from the Latin past participle of conficere, meaning “to prepare or make ready.” Passed through Old French, the root word took on the sense of “preserving”—hence the French confit andconfiture, meaning, respectively, “preserved meat” and “preserved fruit,” i.e., jam. In the wake of the discovery of the New World and the intensive cultivation of sugar cane on slave plantations in the tropical Americas, the dominant meaning of confit and its pan-European cognates came to becandying—cooking in sugar. Confetti, in eighteenth-century Italian, thus meant “little sweets,” the kind of thing an Englishman might call a “sugarplum,” which is to say, small balls of confect-ionary. Sometimes these consisted of a mince of candied fruit (often encased in a sugar shell—powdered, granulated, panned), and sometimes they were built like a jawbreaker around a kernel of seed (anise, coriander, etc.) or a nut (like what we now call a “Jordan almond”). These were things that could be thrown.
more here.